install: inject kernel arguments for separate /boot during installation

Also need to mount the separate boot partition to `/target/sysroot/boot`
on ostree OS.

Signed-off-by: Huijing Hei <hhei@redhat.com>

Author: HuijingHei

crates/lib/src/install.rs

@@ -758,6 +758,16 @@ async fn initialize_ostree_root(state: &State, root_setup: &RootSetup) -> Result
     // Another implementation: https://github.com/coreos/coreos-assembler/blob/3cd3307904593b3a131b81567b13a4d0b6fe7c90/src/create_disk.sh#L295
     crate::lsm::ensure_dir_labeled(rootfs_dir, "", Some("/".into()), 0o755.into(), sepolicy)?;
 
+    // If we're installing alongside existing ostree and there's a separate boot partition,
+    // we need to mount it to the sysroot's /boot so ostree can write bootloader entries there
+    if has_ostree && root_setup.boot.is_some() {
+        if let Some(boot) = &root_setup.boot {
+            let source_boot = &boot.source;
+            let target_boot = root_setup.physical_root_path.join(BOOT);
+            tracing::debug!("Mount {source_boot} to {target_boot} on ostree");
+            bootc_mount::mount(source_boot, &target_boot)?;
+        }
+    }
     // And also label /boot AKA xbootldr, if it exists
     if rootfs_dir.try_exists("boot")? {
         crate::lsm::ensure_dir_labeled(rootfs_dir, "boot", None, 0o755.into(), sepolicy)?;
@@ -970,6 +980,23 @@ async fn install_container(
         }
     }
 
+    // For seperate /boot filesystem, the better workaround is
+    // to inject kernel arguments during installation.
+    // See discussion in https://github.com/bootc-dev/bootc/issues/1388
+    if let Some(boot) = root_setup.boot.as_ref() {
+        if !boot.source.is_empty() {
+            let mount_extra = format!(
+                "systemd.mount-extra={}:{}:{}:{}",
+                boot.source,
+                boot.target,
+                boot.fstype,
+                boot.options.as_deref().unwrap_or("defaults")
+            );
+            kargs.extend(&Cmdline::from(mount_extra.as_str()));
+            tracing::debug!("Add {mount_extra} to kargs if has seperate /boot");
+        }
+    }
+
     // Finally map into &[&str] for ostree_container
     let kargs_strs: Vec<&str> = kargs.iter_str().collect();
 
@@ -2098,7 +2125,7 @@ pub(crate) async fn install_to_filesystem(
         }
         rootfs_fd
     } else {
-        target_rootfs_fd.clone()
+        target_rootfs_fd.try_clone()?
     };
 
     match fsopts.replace {